1. Field of the Invention
The present invention relates to a method of manufacturing medical implants, and, more particularly, to a method of manufacturing tubular medical implants.
2. Description of the Related Art
Medical implants are manufactured incorporating various techniques to produce different shapes using biologically compatible materials. One medical implant shape that is commonly used is that of a tubular structure. Tubular medical implants have a wide range of medically useful applications in orthopaedics, cardiology and other areas. One useful feature incorporated into tubular medical implants is a pore pattern on the surface and throughout the implant. By incorporating porosity into the tubular implant, the implant can be given useful properties such as controlled therapeutic release and/or an interface for cell or tissue growth.
As cell growth mechanics and pharmacokinetics have become better understood, the pore structure of medical implants have become increasingly complex and structured. Such designs requirements of increased complexity have not been met by current production methods, especially in tubular implants that have a relatively high thickness and/or highly variable pore pattern throughout the implant. Of particular difficulty is varying the implant's pore pattern throughout the thickness of the tubular implant.
One known method of producing tubular medical implants with varied porous structures is to take a base tube, such as a stent, and stretch an elastic, porous graft material over the stent. When the graft material is properly positioned over the tube, the stretching force is removed which allows the graft material to return to a less stretched state and form a snug fit on the stent. The graft material can then be sewn on to the graft to create a finished stent graft. A problem with this method is that it limits the materials that can be incorporated into the medical implant, is labor intensive and has the risk of permanently changing the pore sizes on the graft material during stretching.
What is needed in the art is a method that can manufacture tubular medical implants that have complex porous structures from a large variety of materials.